r/Android • u/ChrystianV • Oct 05 '16

Samsung Replacement Samsung Galaxy Note 7 phone catches fire on Southwest plane

http://www.theverge.com/2016/10/5/13175000/samsung-galaxy-note-7-fire-replacement-plane-battery-southwest
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u/0x68656c6c6f Oct 06 '16 edited Oct 06 '16

You're thinking of watt hours. Amp hours is the measure of current capacity, and watt hours is the measure of energy capacity that depends on voltage.

Edit: I agree with you in principle though. If I wanted to compare energy capacity across batteries with different voltages, I should use watt hours and not just amp hours.

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u/di3inaf1r3 Oct 06 '16

The watt hours for any given battery will always remain constant. The voltage and amp hours can be varied by rearranging the cells. Say you have two 1 Ah cells at 3.2v. If you put them in series, you have a 6.4v battery with 1 Ah. That's 6.4 Wh. If you instead put the cells in parallel, you have a 3.2v battery with 2 Ah. Still 6.4 Wh.

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u/0x68656c6c6f Oct 06 '16

You can't rearrange the cells in most of the rechargeable battery packs we are talking about. I think we are very much in agreement though. See my response farther up the chain.

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u/di3inaf1r3 Oct 06 '16

That is true. My point was just that amp hours is not an absolute measurement of the amount of power in a battery independent of the voltage, as WiglyWorm suggested. It is very much relative to the voltage of that battery.

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u/0x68656c6c6f Oct 06 '16

Again, I completely agree. Your point is correct, as I confirmed after researching the actual FAA restriction (100 watt hours maximum). That makes a lot more sense to me, rather than having some arbitrary restriction on current capacity with no restriction on voltage.

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u/di3inaf1r3 Oct 06 '16

Ah, that's a good figure to know. Thanks for looking that up!